The present invention is directed to the field of animal nutrition. Specifically, the present invention relates to methods of lowering cholesterol levels in animals and food products derived from animals.
As public awareness of the dangers of cholesterol has increased in recent years, a number of popular food products have drawn criticism for containing high levels of cholesterol. Eggs are among the maligned products that have suffered because of a public perception that eggs are unhealthy. This perception has led to decreased consumption by consumers. Although improved analytical techniques indicate that previous cholesterol levels attributed to eggs were inflated, there is still substantial consumer concern about egg cholesterol.
As a result of concern over cholesterol intake, a market has developed for egg products having reduced cholesterol. Many of these reduced cholesterol products are produced using additional processing steps, which add substantial cost to the production process. For example, U.S. Patent No. 5,780,095 to Jackeschky describes such a process.
Attempts have also been made to reduce egg cholesterol by modifying the feed given to the egg-producing animals. For example, fibrous feed ingredients, such as barley, and feed additives, such as copper, wood shavings and human cholesterol reducing agents have been utilized in an effort to reduce egg cholesterol. These feeds have proven disadvantageous for a number of reasons. Unlike corn, barley is not a major cereal source in the United States. Thus, the use of barley increases feed costs. Additionally, the production rate of barley may be insufficient to provide a reliable feed supply. Supplementary feed additives, such as copper, increase feed costs and occupy valuable space during the feed mixing process and increased environmental contamination.
There remains a need in the art for a method of lowering the cholesterol levels in animals and eggs without requiring substantial additional process steps or requiring expensive feed additives.
The present invention provides a method of reducing cholesterol in animals and food products derived from such animals. The method includes feeding the animals a low phytate food source so that the phytate phosphorus intake of the animal is reduced. Supplying a food source containing reduced levels of phytate phosphorus decreases the cholesterol level in the animal and in the food products, such as eggs, produced by the animal.
As used herein, xe2x80x9cfood sourcexe2x80x9d refers to sources that provide a substantial portion of the nutritional and caloric requirements of the animal, rather than sources, such as mineral supplements, that provide limited nutritional and caloric value. For example, food sources useful in the present invention include soybeans or cereal grains such as corn, sorghum, barley, rye, wheat, rice, millet, processed products derived from the above or mixtures thereof. As used herein, xe2x80x9ctotal animal dietxe2x80x9d refers to the complete animal diet, including the food sources described above as well as one or more supplements, such as vitamin and mineral supplements, added fat, medications, and the like.
Specifically, the method of reducing cholesterol comprises providing a food source, wherein the food source comprises less than about 0.30 weight percent phytate phosphorus on an as is basis for soybeans, and less than 0.19 weight percent phytate phosphorus on an as is basis for other food sources. The food source is fed to the animal such that the cholesterol of the animal is reduced. The animal may be any animal that would benefit from a reduction of cholesterol.
A method of producing eggs having reduced cholesterol is also provided. The method includes providing a food source as described above, feeding the food source to an egg-producing animal and collecting at least one egg produced by the animal.
The egg yolks produced by the above method have at least about 8% less total cholesterol as compared to a normal egg yolk, preferably at least 15% less total cholesterol, and most preferably at least 20% less total cholesterol. Similarly, eggs produced by the above process have at least about 6% less low density lipoprotein as compared to a normal egg and preferably at least about 15% less low density lipoprotein.
The present invention now will be described more fully hereinafter. However, the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
The present invention is directed to a method of reducing cholesterol in animals, including non-ruminant and ruminant animals, as well as a method of reducing the cholesterol level in food products derived from such animals, such as meat, milk, and eggs. The term xe2x80x9cnon ruminantxe2x80x9d animals includes, but is not limited to, dogs, cats, humans, swine, and poultry, such as chickens, turkeys, etc. Ruminant animals, such as cattle and sheep, may also benefit from the present invention.
Phosphorus is an essential dietary ingredient for maintaining animal health. The phosphorus content in animal food sources, such as corn, may be divided into two types: available phosphorus and phytate phosphorus. Available phosphorus is that portion of the phosphorus content that may be metabolized and used by animals.
The majority of phosphorus found in many animal food sources, such as corn and soybeans, is in the form of phytate phosphorus. For example, phytate phosphorus accounts for approximately 65% of total phosphorus found in many cereal grains (and more than 80% in corn). Monogastric animals, such as poultry, do not possess the necessary phytase enzymes in quantities that would allow these animals to utilize phytate phosphorus as a source of phosphorus. As a result, the diets of many food-producing animals are supplemented with additional amounts of phosphorus, such as dicalcium phosphate, to encourage normal growth and development. It has been noted that the increased level of phosphorus in the diets of these animals presents phosphorus run-off problems on land fertilized with animal manure.
In order to reduce the phosphorus run-off problem, it is proposed to feed animals food sources which have low amounts of phytate phosphorus either in the form of naturally-occurring low phytate food sources or in the form of specially bred or genetically altered food sources.
A low phytate phosphorus corn mutation has been developed by the USDA and is disclosed in U.S. Pat. No. 5,689,054 to Raboy, which is herein incorporated by reference in its entirety. Additionally, U.S. application Ser. No. 09/118,442, filed on Aug. 17, 1998 and assigned to the same Assignee as the present invention, is directed to the identification and use of genes encoding various enzymes involved in the metabolism of phytate in plants and the use of these genes and mutants thereof to reduce the levels of phytate and/or increase the levels of available phosphorus in food sources. The above-described patent application is herein incorporated by reference in its entirety. Low phytate soybeans are disclosed in WO 98/45448.
Surprisingly, it has been discovered that low phytate phosphorus food sources also serve to reduce cholesterol levels in the animals, as well as in food products produced by the animals. For example, it has been shown that low phytate food sources reduce serum and meat cholesterol levels, as well as cholesterol levels in eggs. This is particularly surprising in light of studies conducted with rats indicating that dietary phytate either reduces serum cholesterol levels or has no effect at all. See Katayama et al., Biosci. Biotech. Biochem., 59 (6), 1159-1160 (1995).
As evidenced by the above-described patent and patent application, phytate phosphorus levels can be altered by breeding or genetic manipulation. The low phytate phosphorus food source used in the present invention has a phytate phosphorus concentration that will depend on the origin of the food source. Low phytate soybeans generally have less than about 0.30 weight percent phytate phosphorus on an as is basis. Low phytate corn generally has less than about 0.19 weight percent phytate phosphorus on an as is basis, preferably less than about 0.17 weight percent, and most preferably less than about 0.15 weight percent.
The total animal diet will generally contain between about 0.10 and about 1.00 weight percent available phosphorus on an as is basis, preferably between about 0.10 and about 0.80 weight percent, more preferably between about 0.20 and about 0.65 weight percent, and most preferably between about 0.20 and about 0.50 weight percent.
The total animal diet will generally contain between about 0.10 and about 1.20 weight percent total phosphorus on an as is basis, preferably between about 0.20 and about 1.00 weight percent total phosphorus, more preferably between about 0.20 and 0.95, and most preferably between about 0.30 and about 0.70 weight percent.
In one embodiment, the low phytate food source of the present invention comprises both a low phytate cereal food source, such as low phytate corn, and a low phytate protein source, such as low phytate full fat soybeans or low phytate soybean meal. The relative amounts of the protein source and the cereal source will vary depending on a number of factors, including the age and type of animal being fed. If a mixture of food sources is used, generally the cereal low phytate food source comprises at least about 30% by weight of the total animal diet, preferably at least about 40%, more preferably at least about 50%. In one embodiment, the cereal low phytate food source comprises about 50% to about 80% of the total animal diet. If a low phytate protein source is used in the food source mixture, generally it comprises at least about 5% of the total animal diet, preferably about 10% to about 55%, more preferably about 15% to about 30%. Processed products derived from cereal grains and/or oil feeds may be present in an amount of from about 1% to about 30% of the total animal diet. Examples of such processed products include corn gluten meal, corn gluten feed, canola meal and the like.
In another embodiment of the present invention, a reduction in cholesterol level is achieved by using a food source having both a decreased phytate phosphorus concentration and increased oil concentration. The oil concentration is increased by an amount sufficient to reduce the cholesterol level of an animal fed the food source as a substantial part of a total animal diet. In a preferred embodiment, the oil concentration of the food source, such as corn, is increased by adding at least one fatty acid, including, but not limited to, palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, arachidic acid, eicosenoic acid, behenic acid, and lignoceric acid. Preferably, the oil content of the low phytate food source is about 5% to about 15% by dry weight, more preferably about 6% to about 10%, most preferably about 7 to about 8%.
The method of the present invention includes providing a food source containing decreased levels of phytate phosphorus as described above and feeding that food source to the animal. The method of feeding may be any method known in the art.
The present invention is also directed to an egg having reduced cholesterol as compared to a normal egg. In this regard, a xe2x80x9cnormal eggxe2x80x9d is defined as an egg produced by an animal fed conventional food sources containing conventional forms and amounts of phosphorus. By reduced cholesterol is meant lower cholesterol concentration. The actual amount of cholesterol in a normal egg varies with the age and diet of the egg-producing animal. As an example, on day 28 of the study described in Example 1, the average total cholesterol level of the egg yolks produced by the control group of animals being fed conventional corn feed was approximately 1.158 grams/100 grams of yolk. Additionally, in the same study, the control group of animals produced an average egg yolk total cholesterol level of approximately 1.494 grams/100 grams of yolk on day 140 of the study.
The present invention provides a method of reducing total cholesterol in an egg by about 5 to about 50 percent as compared to a normal egg. In some embodiments, the range of total cholesterol reduction is about 5 to about 30 percent or 5 to about 25 percent. For example, in the study described in Example 1, the eggs collected from the animals being fed the low phytate food source had a reduced total cholesterol level of at least about 8% below the egg total cholesterol level of the control group on the same day, preferably at least about 13% as much, more preferably at least about 15% and even as much as about 20% or 23% less total cholesterol. Further, the eggs collected from the animals fed the low phytate food sources exhibited a low density lipoprotein of at least about 4% or about 6% below that of the normal eggs collected from the control group, and as much as about 15% or 22% or more below that of the normal eggs in the control group.
These reductions in cholesterol levels are achieved using the method of the present invention without further post-laying processing steps and without expensive feed additives. As a result, the term egg, as used herein, is intended to mean an egg product substantially free of post-laying treatment or processing designed to reduce the cholesterol level of the egg.